Academic literature on the topic 'Microplastics ingestion'

Microplastics (less than 5 mm) are a recognized threat to aquatic food webs because they are ingested at multiple trophic levels and may bioaccumulate. In urban coastal environments, high densities of microplastics may disrupt nutritional intake. However, behavioural dynamics and consequences of microparticle ingestion are still poorly understood. As filter or suspension feeders, benthic marine invertebrates are vulnerable to microplastic ingestion. We explored microplastic ingestion by the temperate coral Astrangia poculata . We detected an average of over 100 microplastic particles per polyp in wild-captured colonies from Rhode Island. In the laboratory, corals were fed microbeads to characterize ingestion preference and retention of microplastics and consequences on feeding behaviour. Corals were fed biofilmed microplastics to test whether plastics serve as vectors for microbes. Ingested microplastics were apparent within the mesenterial tissues of the gastrovascular cavity. Corals preferred microplastic beads and declined subsequent offerings of brine shrimp eggs of the same diameter, suggesting that microplastic ingestion can inhibit food intake. The corals co-ingested Escherichia coli cells with microbeads. These findings detail specific mechanisms by which microplastics threaten corals, but also hint that the coral A. poculata , which has a large coastal range, may serve as a useful bioindicator and monitoring tool for microplastic pollution.

Abstract Microplastics in the marine environment are well documented, and interactions with marine biota have been described worldwide. However, interactions with vertically migrating fish are poorly understood. The diel vertical migration of mesopelagic fish represents one, if not the largest, vertical migration of biomass on the planet, and is thus an important link between the euphotic zone, transporting carbon and other nutrients to global deep sea communities. Knowledge of how mesopelagic fish interact and distribute plastic as a marine contaminant is required as these populations have been identified as a potential global industrial fishery for fishmeal production. Ingestion of microplastic by mesopelagic fish in the Northeast Atlantic was studied. Approximately 11% of the 761 fish examined had microplastics present in their digestive tracts. No clear difference in ingestion frequency was identified between species, location, migration behaviour, or time of capture. While ingesting microplastic may not negatively impact individual mesopelagic fish, the movement of mesopelagic fish from the euphotic zone to deeper waters could mediate transfer of microplastics to otherwise unexposed species and regions of the world's oceans.

Over the past decade, concerns over microplastic pollution in the marine ecosystem has increasingly gained more attention, but research investigating the ingestion of microplastics by marine fish in Malaysia is still regrettably lacking. This study investigated the microplastic presence, abundance, and morphological types within the guts of four species of commercial marine fish (Atule mate, Crenimugil seheli, Sardinella fimbriata and Rastrelliger brachysoma) caught in seawater off the coast of Malaysia’s Northwest Peninsular. A total of 72 individual commercial marine fish guts from four species (fish per species n = 18) were examined. Remarkably, this study found that 100% of the samples contained microplastics. A total number of 432 microplastics (size < 5 mm) from the four species were found in the excised marine fish guts. The most common type of microplastic discovered was fragment, which accounted for 49.5% of all microplastics present. The gut microplastic content differed between species. Sardinella fimbriata recorded the greatest amount of microplastic ingestion, with an average microplastic count of 6.5 (±4.3) items per individual fish. However, there were no statistically significant differences found when comparing study species and different locations. SEM-EDX analysis confirmed the presence of microplastic particles by identifying the chemical elements found in the samples. Since the four studied species of commercial marine fish are popular protein sources in Malaysians’ daily diet, this study suggests potential microplastic exposure to humans via contaminated fish consumption in Malaysia, which was previously unknown. Based on previous scientific evidence, this study also demonstrates the high probability of microplastic ingestion in marine fish in the Malaysian seawater, which could have an adverse effect on fish health as well as marine biota.

This study aims to review the occurrence of microplastics in some commercial aquatic organisms. Microplastics are small plastic particles with a diameter of less than 5 mm. Effluent, stormwater, agricultural, and surface runoff introduce microplastic to freshwater basins. Hydrodynamics and hydrology encompass microplastics. River flow speed can cause turbulence and riverbed instability, increasing microplastic concentrations. Fish, shellfish, and crustaceans ingest microplastics in proportion to their quantity in freshwater and marine environments. Human activities cause variations in the form, color, and size of microplastics in the biota. Animals absorb microplastics through trophic transfer. Increased microplastic residence time before ingestion promotes trophic transmission. Lower food concentration and aggregation enhance microplastic retention in zooplankton guts, increasing transmission to higher-trophic-level species. Most studies show that microplastics in biota are discovered in fish and crustacean intestines and bivalve tissues. Microplastic buildup can disrupt live organisms' growth and reproduction, induce oxidative stress, obstruct the digestive system, and damage the intestine. Microplastics may harm people's health if they eat contaminated seafood that contains them, but more research is needed.

Microplastic debris is a persistent, ubiquitous global pollutant in oceans, estuaries, and freshwater systems. Some of the highest reported concentrations of microplastics, globally, are in the Gulf of Mexico (GoM), which is home to the majority of plastic manufacturers in the United States. A comprehensive understanding of the risk microplastics pose to wildlife is critical to the development of scientifically sound mitigation and policy initiatives. In this review, we synthesize existing knowledge of microplastic debris in the Gulf of Mexico and its effects on birds and make recommendations for further research. The current state of knowledge suggests that microplastics are widespread in the marine environment, come from known sources, and have the potential to be a major ecotoxicological concern for wild birds, especially in areas of high concentration such as the GoM. However, data for GoM birds are currently lacking regarding typical microplastic ingestion rates uptake of chemicals associated with plastics by avian tissues; and physiological, behavioral, and fitness consequences of microplastic ingestion. Filling these knowledge gaps is essential to understand the hazard microplastics pose to wild birds, and to the creation of effective policy actions and widespread mitigation measures to curb this emerging threat to wildlife.

This literature review exploring the relationship between microplastics and ichthyoplankton was conducted in the main databases available online, considering the period from 2007 to 2021. Sixty articles were found reporting the presence of microplastics in estuarine environments (71.7%), and ingestion by ichthyoplankton in estuarine environments (16.6%) and under experimental conditions (11.7%). The most abundant microplastic found in natural environments was fiber (55%). Environments with densities between 17.5 and 4100 particles/m³ exhibited greater possibilities of ingestion of these particles by ichthyoplankton, the smaller the microplastic particle (63 μm-0.5 mm) the greater the probability (95%) of being ingested by ichthyoplankton (>2.56 mm). Danio rerio (zebrafish) was the species commonly used to assess the effects caused by the interaction between microplastics and ichthyoplankton under experimental conditions. The effects frequently reported were: increased heart rates (25%); growth inhibition (25%); interference in larvae’s swimming speed (53.4%); and inflammation in various organs (e.g., liver, intestine) (50%).

Marine microplastic has been in the limelight recently. This study aimed to describe microplastic types ingested by 274 fish from Thailand’s eastern coast in 2020 and to compare the microplastic content among different feeding traits. The microplastics in the gastrointestinal tracts and gills were extracted, analyzed, and identified using FT-IR spectroscopy. Approximately 13.14% of the total specimen ingested microplastics, with an average of 0.14 items per individual. The detection frequency of microplastics was relatively high compared with other regions in Thailand but relatively low compared to global standards. Of the microplastic contaminated specimens, 56.41% had at least one piece of microplastic in their gastrointestinal tract. Pelagic (14.47%) species were found to have ingested more microplastics than the demersal (12.63%) group. Dominant aspects found included PET (as in polymers), fiber (as in shape), and black (as in color). However, microplastic numbers fluctuated with the size, weight, and feeding behavior of fish. This result suggested that the pelagic has a higher exposure risk and microplastic ingestion in relatively small quantities in a range of fish species. Our results indicated that the occurrence of microplastics in fish is not influenced by organism habitat or trophic level, although the characteristics of pelagic fish might significantly increase the chance of exposure to microplastics in pelagic species.

Microplastic contamination has been considered as a global environmental problem in marine ecosystem. Due to small size (< 5 mm) in overlapping with that of microalgae, microplastics can easily be ingested by a wide range of marine copepods. Microplastics are mistakenly ingested by zooplankton as food, subsequently disrupting the biological process of zooplankton, a crucial food source for many secondary consumers. As copepods dominate zooplankton biomass and provide an essential trophic link in marine ecosystem, copepods are at an increased risk of microplastic ingestion. The seasonal change in microplastics in copepods and the key environmental factors influencing the retention of microplastics in copepods are largely unknown. In the present study we collected copepods from Ennore estuary and identified them up to the species level. The samples were digested and visually examined by using microscope for presence of microplastic. Our results showed that the copepods collected from Ennore estuary contained microplastics in their body.

Marine plastic pollution is currently an issue of mounting concern around the world. Stomach content of marine fish has been increasingly used as a valid proxy for detecting the presence of such a pollutant in marine biota, both for coastal and deep-water environments. Although ingestion of microplastics has been reported in an increasing number of species, the patterns of ingestion still remain unclear, depending closely on the interaction between the species and types of microplastics involved. In this context, we analysed and compared the stomach contents of two bathyal dwelling opportunistic feeder species namely Galeus melastomus and Coelorinchus caelorhincus. In particular, we analysed microplastic items according to their dimension, morphology and colour, and diet’s variation with size obtained through prey identification. Both species showed a higher frequency of occurrence of the blue filament-like middle-sized microplastics (1.01–4.75 mm) compared with the other categories, although this pattern was much more marked in C. caelorhincus than in G. melastomus. The latter conversely showed a larger array of ingested plastic items in terms of shape and colour. Matching plastic ingestion with dietary data suggested potential predator confusion occurring in C. caelorhincus through active mis-selection of a defined type of microplastic instead of some particular family of polychaetes, which resemble in shape, size, and color to that type. Otherwise, G. melastomus appeared more prone to a random ingestion of a larger array of microplastic items because of a more generalistic and less selective feeding strategy. Although further validation is needed, stomach contents of the two species showed evidence strong enough to be considered as potential bioindicator species of microplastic pollution, as required by the Marine Strategy Framework Directive for monitoring this pollutant in the marine environment.

As microplastic pollution continues to increase, an emerging threat is the potential for microplastics to act as novel substrates and/or carriers for pathogens. This is of particular concern for aquatic product safety given the growing evidence of microplastic ingestion by aquaculture species. However, the potential risks of pathogens associated with microplastics in mariculture remain poorly understood. Here, an in situ incubation experiment involving three typical microplastics including polyethylene terephthalate (PET), polyethylene (PE), and polypropylene (PP) was conducted during the summer–autumn period in a mariculture cage. The identification of potential pathogens based on the 16S rRNA gene amplicon sequencing and a custom-made database for pathogenic bacteria involved in aquatic environments, was performed to assess the risks of different microplastics attaching potential pathogens. The enrichment of pathogens was not observed in microplastic-associated communities when compared with free-living and particle-attached communities in surrounding seawater. Despite the lower relative abundance, pathogens showed different preferences for three microplastic substrates, of which PET was the most favored by pathogens, especially potentially pathogenic members of Vibrio, Tenacibaculum, and Escherichia. Moreover, the colonization of these pathogens on microplastics was strongly affected by environmental factors (e.g., temperature, nitrite). Our results provide insights into the ecological risks of microplastics in mariculture industry.

A discrepancy between high plastic production rates and low recycling rates contributes to a ubiquitous plastic pollution problem. If this discrepancy persists, it is estimated that approximately 12 billion tons of plastics will accumulate in the environment by 2050. Although many countries have issued policies to limit the utilisation of single use plastics, the COVID-19 pandemic has increased demands for plastics and overwhelmed waste management systems. Thus, plastic pollution will persist, especially in marine environments where most mismanaged plastics accumulate. Plastics in the marine environment slowly disintegrate into microplastics (<5 mm) and adversely affect many animals when ingested. Thus, microplastics have recently been identified as an emerging contaminant of concern internationally, resulting in an exponential growth in the number of microplastic studies within the last decade. Studies in some ecologically important animals such as jellyfish, however, are preliminary. For example, jellyfish are claimed to ingest microplastics via trophic transfer and have been promoted as bioindicators for plastic pollution despite limited evidence. Moreover, although microplastics in the field are covered by biofilms, all jellyfish and microplastic experiments have used virgin microbeads that might underestimate ingestion rates. This thesis, therefore, tested three hypotheses: 1) that jellyfish would ingest microplastics and they would be adversely affected by microplastic ingestion (chapter 2), 2) that jellyfish would mainly accumulate microplastics via indirect ingestion (i.e. trophic transfer) and biofilms would promote ingestion rates (chapter 3), 3) that jellyfish would be useful bioindicators of microplastic pollution and treated wastewater would be a significant source of microplastics in an estuary (chapter 4). Medusae of Aurelia coerulea were exposed to 2,000 polystyrene microbeads L-1 and determined numbers of microbeads ingested. In addition, impacts of microbead ingestion on respiration rates and histology of their gut tissues were assessed (Chapter 2). No tissue damage was observed and respiration rates were unaffected by ingestion of microbeads. Importantly, the medusae ingested less than 0.2% of microbeads offered, egested microbeads within eight hours and stopped ingesting the microbeads after 16 hours, suggesting that the medusae may recognise virgin microbeads as non-food items. I, therefore, exposed the medusae to microbeads with photosynthetic biofilms, microbeads with heterotrophic biofilms and virgin microbeads (Chapter 3). Medusae ingested more microbeads with photosynthetic biofilms than microbeads with heterotrophic biofilms or virgin microbeads. The results highlight that the use of aged microbeads in experiments is important as the ingestion rates may be underestimated if virgin microbeads are used. Although jellyfish are claimed to acquire microbeads via trophic transfer, no studies had tested whether trophic transfer is a dominant pathway as jellyfish can also ingest microplastics directly from their surrounding water. Thus, I exposed ephyrae of Aurelia coerulea to aged microbeads (to test direct ingestion) and to Artemia nauplii fed aged microbeads (to test trophic transfer), and quantifued numbers of microbeads in the gastrovascular cavities (Chapter 3). I found that the ephyrae ingested 35 times more microbeads via trophic transfer than direct ingestion, suggesting that trophic transfer is the primary pathway by which jellyfish acquire microbeads. Furthermore, I investigated whether jellyfish in the field are susceptible to microplastic ingestion and whether jellyfish can be bioindicators of microplastic pollution. Water samples and medusae of Chrysaora cf pentostoma were collected nearby and distant from treated wastewater diffusers in two estuaries (the Gold Coast Broadwater and the Tweed River Estuary) that receive contrasting amounts of wastewater, to test whether microplastics in the guts of medusae represented those in the environment (Chapter 4). Only 83% of the medusae sampled contained microplastics and types and colours of microplastics in the gastrovascular cavities of jellyfish differed to those in the surrounding water. Thus, medusae are not good bioindicators of microplastic pollution because not all medusae acquire microplastics and the microplastics they accumulated did not reflect those in their environment. I also tested whether the released treated wastewater would have significant effects on microplastic concentrations and compositions in the receiving waters of the estuaries as wastewater treatment plants are claimed to be one of the significant sources of microplastics. I found no significant difference between microplastic concentrations and compositions nearby and distant from wastewater releases in either estuary. Thus, treated wastewater had no detectable impacts on microplastic concentrations and compositions in the receiving waters. Results from both laboratory and field experiments (Chapter2; Chapter 3; Chapter 4) strongly indicated that jellyfish accumulate relativly small amounts of microplastics and are poor bioindicators for microplastic pollution.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
Full Text

This thesis presents: 1) the first statistically rigorous support for the longstanding hypothesis that state of satiation modifies diel vertical migration patterns of deep-sea micronektonic crustaceans and fishes; and, 2) the first assessment of microplastic ingestion by deep-pelagic micronekton in the Gulf of Mexico and Straits of Florida. Deep-sea pelagic crustaceans and fishes significantly contribute to abundance and biomass of pelagic ecosystems, are frequently consumed by commercially valuable fishery species, and serve to transport both nutrients and pollutants between shallow and deep waters. The results presented herein will be valuable for assessing risk associated with potential biomagnification of plastic through consumption or indirect consumption of deep-sea biota. Moreover, these data demonstrate that the extent of feeding at depth by non-migratory taxa as well as non-migrating individuals of migratory taxa is substantial. Feeding at depth is usually excluded from biogeochemical models, and these data demonstrate that this is an important factor that must be included to obtain more precise estimates of active nutrient flux by micronekton.

Microplastic pollution (particles < 5mm) is one of the most widespread impacts from modern society. Here, microplastic impacts were investigated through experimental assessments considering different exposure scenarios using mussels and micro-PVC as models. These aimed to investigate mussels\' physiological signs of stress under acute and chronic exposures and microplastics transference, assimilation and retention along food chains. In acute exposures, PVC intake affected mussels\' physiology over time, also influenced by plastics additives and particle concentration. Interactions among exposure factors (time, presence of additives and concentration) were more relevant than their individual effect, indicating the singularity of each contamination scenario. Long-term contact did not affect mussels, indicating the influence of time to acclimation. Microplastics were not assimilated and retained along food chains, but only biotransferred from prey tissues to predators\' tract, showing the influence of prey contamination on the effectiveness of microplastics biotransference. To evaluate risks in nature, microplastic ingestion was investigated in mussels from the Santos Estuary. Santos Estuary contained microplastics in 75% of sampled mussels, an issue of environmental and human concern. This study illustrated that microplastics impacts on mussels vary with microplastics characteristics, exposure scenario and species vulnerability, highlighting the need for more toxicological and risk evaluation studies.
Os microplásticos (< 5mm) são um dos impactos mais difundidos da sociedade moderna. Aqui, eles foram estudados em ensaios experimentais, considerando diferentes composições de exposição de mexilhões à micro-PVCs. O objetivo foi investigar: sinais fisiológicos de estresse sob exposições aguda e crônica; e transferência, assimilação e retenção de microplásticos em cadeias tróficas. Para avaliar seus potenciais riscos na natureza, a ingestão por mexilhões também foi investigada no Estuário de Santos. As exposições agudas afetaram a fisiologia dos mexilhões, sendo influenciadas pelo tempo e concentração de exposição, e pela presença de aditivos plásticos. Interações entre esses fatores (tempo, concentração e aditivos) foram mais relevantes do que eles individualmente, sugerindo a singularidade dos cenários de poluição. A exposição de longo prazo não afetou os mexilhões, indicando a influência do tempo na aclimatação ao microplástico. O PVC não foi assimilado e retido nas cadeias tróficas, mas biotransferido do tecido das presas para o trato dos predadores, mostrando a influência do estado da presa na efetividade da biotransferência dos microplásticos. Dentre os mexilhões coletados, 75% estavam contaminados, revelando uma importante questão socioambiental. Esse trabalho ilustrou a complexidade dos impactos dos microplásticos para a biota marinha, ressaltando a necessidade de mais estudos sobre seus riscos.

Microplastics can be defined as “any synthetic solid particle or polymeric matrix, with regular or irregular shape and with size ranging from 1 μm to 5 mm, of either primary or secondary manufacturing origin, which are insoluble in water”. The growing demand and consequent production of plastic products both at microscale (e.g., personal care products) and at macroscale with inappropriate disposal subsequent degradation in the environment has turned microplastics into global emergent pollutants of the aquatic environment. In fact, the levels of microplastics that have been found in river and lake sediments, raise concern about ingestion and potential negatives effects of microplastics in aquatic benthic invertebrates, particularly those who feed on particulate matter. Possible effects at different levels of biological organisation (sub -organismal up to community level s) are still overlooked , as well as the study of the toxic effects of microplastics to invertebrate biota under relevant exposure scenarios, especially considering climatic change. Therefore, the objective of this thesis was to evaluate the effects of irregularly shaped pol y ethylene microplastics (one of the polymer type microplastics most produced and found in aquatic sediments) using a holistic approach that combines sub -organismal, organismal, population and community level responses, aiming to produce relevant ecotoxicol o gical data for risk assessment of microplastics in freshwaters. First, a quantitative and qualitative assessment of the ingestion of microplastics was evaluated in two model aquatic species, the dipteran Chironomus riparius and the endobenthic oligochaet e Lumbriculus variegatus, as these species feed on particulate matter, being prone to ingest microplastics. Along with the assessment of the ingestion of microplastics, the effects (both at sub -cellular and organismal level) were assessed in an attempt to link ingestion and potential deleterious effects induced by the particles per se. Activation of immune response (phenoloxidase activity), oxidative stress and damage , as well as , effects on life -history traits (larval growth and development) , were observed in C. ripariu s and associated to the augmented ingestion and retention of microplastics in their gut when compared to L. variegatus, which only presented slight evidence of oxidative stress and no effects on reproduction. The combined exposure of microplastics with natural stressors was then performed in Chironomus riparius (the most sensitive species ). Temperature, salinity and food shortage were used as natural stressors relevant under climate change scenarios and that could modulate the ingestion and induced effects of microplastics in relevant exposure scenario s . The results show that interactions between microplastics exposure and these natural stressors are complex and mainly additive and antagonistic effects were observed. However, results also identified conditions (low temperatures and severe food shortage) where sub - lethal effects of MPs to natural populations of C. riparius can be stronger than predicted by standard toxicity assays. These combined exposures revealed that under different environmental conditions, toxicity of MPs is not simply a reflection of internal concentrations of particles. Conceivably the main research gap that subsists is the investigation on the ecological effects of microplastics. For that purpose, this thesis performed a mesocosms approach addressing the effects at the community structure and ecosystem functioning, vital to deliver higher - tier risk assessments . This higher -tier approach (i.e., using artificial streams inoculated with natural benthic invertebrate communities) showed that the exposure to a pool of different -sized polyethylene microplastics affected the macroinvertebrate community structure, mainly by reducing the abundance of deposit -feeders and grazers. The ingestion of microplastics by different invertebrate feeding groups correlated positively with the effects as deposit -feeders and grazers presented the higher number of microplastics inside the organisms’ guts. A slight reduction in primary production was observed and may be a possible direct effect of microplastics on periphyton growth. Only slight effects were observed in terms of leaf litter decomposition signalling that the exposure to polyethylene microplastics might not have affected feeding behaviour of shredders or in turn that exposure period was too short to reveal trait -mediated indirect effects . In conclusion, the present thesis demonstrates that microplastics can be ingested by some aquatic macroinvertebrates and that enhanced ingestion can potentially pose a risk to natural invertebrates’ population. Despite considerable interspecific variation in sensitivity to polyethylene microplastics, their presence in sediments can alter community structure and represent a risk to ecosystem functioning at the long -term. The present thesis confirms that immune responses and oxidative stress as key molecular initiating event s in microplastic toxicity, shows that assessing the internal concentrations of plastic particles is critical for a correct evaluation of effects in biota and highlights the need to incorporate more invertebrate species and relevant exposure conditions for an accurate risk assessment of microplastics in freshwaters.
Os microplásticos podem ser definidos como “qualquer partícula sólida de origem sintética ou matriz polimérica, de forma regular ou irregular e com tamanho entre 1 μm to 5 mm, tanto de origem de produção primária como secundária e que são insolúveis em água”. A crescente procura por este tipo de produtos e consequentemente a sua maior produção, tanto à microescala (p. ex.: produtos de higiene pessoal), como à macroescala com descarte incorreto e consequente degradação no meio ambiente, tornaram os microplásticos num poluente emergente do ambiente aquático à escala global. Assim sendo, os níveis de microplásticos que têm vindo a ser encontrados nos sedimentos de rios e lagos geram preocupação acrescida relativamente à sua potencial ingestão e efeitos gerados por esta em invertebrados bentónicos, particularmente aqueles que se alimentam de matéria orgânica particulada. Existe ainda pouca informação relativamente aos possíveis efeitos provocados pelos microplásticos nos diversos níveis de organização biológica (desde o nível suborganismal até à comunidade), bem como, em relação aos efeitos dos microplásticos em invertebrados sob cenários relevantes de exposição, em especial considerando as alterações climáticas. Assim, o principal objetivo desta tese foi o de avaliar os efeitos de microplásticos com forma irregular de polietileno (um dos polímeros mais produzidos no mundo e também dos mais encontrados nos sedimentos de rios e lagos), usando uma abordagem holística que combina respostas ao nível sub-organismal, organismal, populacional e da comunidade, pretendendo deste modo facultar informação ecotoxicológica relevante que possa ser usada na avaliação de risco dos microplásticos em ambientes dulçaquícolas. Para tal, a ingestão de microplásticos foi avaliada em termos quantitavos e qualitativos em duas espécies bentónicas -modelo, o díptero Chironomus riparius e o oligoqueta Lumbriculus variegatus, que sendo espécies que se alimentam de matéria particulada, estarão mais suscetíveis à ingestão de microplásticos. Paralelamente à avaliação da ingestão de microplásticos, foram também avaliados os efeitos (tanto a nível sub-celular como ao nível do organismo) numa perspetiva de relacionar ingestão e efeitos. Os principais efeitos observados prenderam-se assim com a ativação da resposta imune (medida através da atividade da fenoloxidase), stress e dano oxidativo, bem como efeitos ao nível do ciclo de vida em C. riparius (diminuição do crescimento larvar e atraso no desenvolvimento). Estes efeitos foram assim relacionados com a maior ingestão de microplásticos, quando comparada com a ingestão observada em L. variegatus, que somente apresentou sinais ligeiros de stress oxidativo e ausência de efeitos na reprodução. A espécie mais sensível, Chironomus riparius, foi então exposta a microplásticos em combinação com diversos stressores naturais. Os stressores naturais escolhidos foram a temperatura, salinidade e limitação da disponibilidade de alimento, sendo estes relevantes em cenários de alterações climáticas, e capazes de alterar a ingestão e consequentemente os efeitos provocados pelos microplásticos. Os resultados demonstram que as interações decorrentes da exposição conjunta de microplásticos com os stressores naturais são complexas, sendo que os efeitos observados foram maioritariamente aditivos ou antagonísticos. Contudo, sob determinadas condições como baixa temperatura e significativa limitação da disponibilidade de alimento, os efeitos sub -letais dos microplásticos nas populações naturais de C. riparius poderão ser mais severos que o previsto pelos ensaios ecotoxicológicos padronizados. Estes efeitos combinados revelaram ainda, que sob determinadas condições ambientais, os efeitos tóxicos dos microplásticos poderão não ser simplesmente um reflexo das concentrações de microplásticos encontrada s no interior dos organismos. A avaliação dos efeitos ecológicos da exposição a microplásticos é possivelmente , a principal lacuna que subsiste na investigação. Assim, esta tese procurou colmatar essa lacuna, com recurso a um ensaio usando rios artificiais (mesocosmos), em que foram estudados os efeitos na estrutura da comunidade de invertebrados bentónicos, bem como nas funções providenciadas pelo ecossistema, vitais para uma melhor avaliação de risco. Esta abordagem demonstrou que a exposição a microplásticos de polietileno de diversos tamanhos afetou a estrutura da comunidade, sobretudo através da redução da abundâ ncia de invertebrados coletores de depósito e raspadores. A ingestão de microplásticos pelos diferentes grupos funcionais de invertebrados correlacionou -se positivamente com os efeitos, uma vez que coletores de depósito e raspadores apresentaram o maior número de microplásticos no seu interior . Foi ainda observada uma ligeira redução na produção primária que poderá estar relacionada com um efeito direto dos microplásticos no crescimento do perifíton. De igual modo, observou -se apenas uma ligeira redução na decomposição da folhada, sendo este efeito indicativo de que a exposição a microplásticos de polietileno poderá não afetar significativamente o comportamento alimentar dos fragmentadores, ou em alternativa o tempo de exposição poderá ter sido demasiado curto para que estes efeitos indiretos se possam ter manifestado. Em conclusão, a presente tese demonstra que os microplásticos podem ser ingeridos pelos macroinvertebrados de água doce e representar um risco para as populações naturais. Apesar de se ter verificado uma considerável variação interespecífica na sensibilidade aos microplásticos de polietileno, a sua presença nos sedimentos pode alterar a estrutura das comunidades de macroinvertebrados bentónicos e alterar o funcionamento dos ecossistemas a longo prazo. A presente tese comprova também que a resposta imune e o stress oxidativo são eventos -chave de início a nível molecular na toxicidade dos microplásticos, e demonstra que a avaliação das concentrações internas dos microplásticos é crucial para uma correta avaliação dos efeitos nos organismos. Salienta -se ainda a necessidade da incorporação de mais espécies de invertebrados, assim como, de cenários relevantes de exposição para uma avaliação de risco mais precisa dos microplásticos nos ecossistemas dulçaquícolas.
Programa Doutoral em Biologia e Ecologia das Alterações Globais

碩士
國立臺灣海洋大學
食品科學系
107
Due to the extensive use of plastic products by humans in daily life, microplastic pollution has become increasingly serious and is now a global environmental problem. Microplastics are plastic fragments less than 5 mm, which are present not only throughout the environment, but also in the daily diet of humans. The purpose of this study was to assess the potential health risks in Taiwan associated with the ingestion of food containing microplastics. We did this by estimating the exposure of Taiwanese people to microplastics through the ingestion of eight food items (beer, honey, salt, sugar, water, fish, shellfish, and crustaceans); establishing the dose–response relationship between microplastics and hepatic total cholesterol (T-CHO) concentration, hepatic triglyceride (TG) concentration, hepatic catalase (CAT) activity, hepatic superoxide dismutase (SOD), cell viability, and effects of reactive oxygen species (ROS) on cells; assessing the potential risk of ingesting microplastics in food by combining the results of the above two analyses; and discussing the relationship between the ingestion of microplastics in food and non-alcoholic fatty liver disease (NAFLD). We used Monte Carlo simulations to model the data and probabilistic analysis to evaluate exposure and the dose-response relationships, and the concept of exceedance risk was used to calculate risk under particular situational conditions. The results of these analyses showed that ingestion of food containing microplastics would not increase hepatic T-CHO concentration, TG concentration, CAT activity, or SOD activity, nor would it cause a deleterious response such as increasing the cell ROS effect. However, it would cause a potential health risk by decreasing cell viability. We also used questionnaires to investigate the risk perception of Taiwanese people regarding food containing microplastics. We collected 460 responses, of which 371 were valid, giving an effective questionnaire recovery rate of 80.7%. The risk perception questions were based on microplastics-related studies, and the five-point Likert scale was used to measure the respondents’ level of agreement, with higher scores indicating a higher level of agreement. The results showed that only 18.6% of the respondents had not previously heard of the term "microplastics", and for 10 out of 14 questions, the scores were higher than the mid-point of the scale, meaning that the respondents generally agreed that their daily diet contained microplastics and that microplastics are harmful to organisms. Thus, Taiwanese people perceive that there are health risks associated with microplastics. As microplastic-related studies are emerging research fields, lack of toxicological information about microplastics for an adequate risk assesseemnt is a major research limitation of this study. Despite many research limitations, this study conducted a preliminary risk assessment on food containing microplastics and investigated the risk perception of Taiwanese people about microplastics, expected to provide an early warning to the government.

The microplastic particles have dramatically increased in marine environments, emerging the concern of their potential adverse effects on marine biota, among others. These biological adverse effects of microplastics may result not only in physical harm such as internal abrasions and blockages, but also in an entrance vector of contaminants into marine organism. Therefore, the overall aim of this study was to assess the health status of two gobies (Blennius pholis and Blennius galerita) exposed to microplastics, both coated and uncoated with antifouling paints (i.e. common source of metals), via feeding for a month. For that purpose, multi-organ histopathological assessment (i.e. gills, liver, kidney and digestive tract) was carried out qualitatively and semi-quantitatively in gobies, as well as histochemical evaluation. The results showed no sign of microplastics ingestion, suggesting that these gobies were not able to ingest used microplastic spheres. Accordingly, no gross histological alterations were recorded in both fish species exposed to microplastics. Similarly, regardless the pathway of contaminants exposure (i.e. by ingestion or waterborne), animals exposed to contaminated microplastics presented similar histopathological levels than those treated with uncontaminated microplastics, or even than control. The affection degree of each target organ revealed gills and liver as the most affected organs following by kidney, digestive tract and spleen. Lamellar lifting, fat vacuolation of hepatocytes and melanomacrophage centers were the most prevalent alterations noticed in gills, liver and whole-body of fish, respectively. These findings may suggest that other factors, even natural occurrence, could be the cause of these mild histopathological alterations. Moreover, the use of Blennius gobies in multi-organ histopathology showed to be a suitable organism and tool for assessing the potential adverse effects caused by microplastics and their potential role as contaminants entrance. Therefore, smaller microplastic particles, both contaminated and uncontaminated, should be tested in gobies in order to clarify and evaluate their potential adverse effects via feeding.

Plastic and microplastics are ubiquitous in the marine environment, their presence and possible ingestion can lead to harmful consequences in the marine environment and biota. To provide a quantification of microplastics ingested by commercial fish from the Portuguese Coastal waters and public awareness of the potential harm to human health, a total of 164 samples of Trachurus trachurus and Scomber colias were collected from Figueira da Foz and Sesimbra fishing ports. After dissection and evaluation, 67% of the individuals were found to have ingested microplastics. A total of 399 microplastics were registered, with an average (mean  SD) of 3.63 ± 3.16 microplastics per contaminated fish. Fibres and fragments were the type of MP found in fish, fibres were recurrently found among individuals, 79% comparing to 21% of fragments. Fish collected from Figueira da Foz fishing port, comprise 62% of the total MPs detected, and, S. colias, the Atlantic mackerel ingested 54% of the total microplastics. Kruskal Wallis H test were performed to identify significant statistical differences between sampled groups and Spearman correlation to link any possible relationship between biometric parameters and number of microplastics ingested per fish. Intra-species comparisons identified significant differences in the number of fibres ingested and in the gastrointestinal tract weights, while inter-species comparisons revealed differences in the amounts of fibres and fragments ingested among individuals. Slight Spearman correlations were registered between the biometric parameters and the number of fibres and fragments ingested.

Marine pollution has attracted increasing attention from scientists and the public in recent years due to its impacts on marine life. Studies have focussed on presence of plastics and metal contaminants in both the water and biota. Links between microplastics and metals in different ares of the environment are often overlooked. Analyses have focussed on many areas of coastal waters and the open ocean but, despite being located within the North Atlantic Gyre, Bermuda has never been studied for plastic presence. Therefore a sequence of impacts of marine pollution were analysed in the water and fishes of Bermuda to provide an overview of the country’s marine pollution situation. Surface trawls were used to determine plastic density in the ocean. This ocean plastic was then evaluated for its bioavailability of metal contaminants. Eight species of fish across three trophic levels were analysed for microplastics present in their guts. Two of these species were selected to investigate the level of metal contaminants in fish tissue. All species and 32% of individual fish contained plastic in their guts. Evidence of biomagnification of microplastics by trophic levels and length was found. Microplastics were confirmed as a vector for metals into fish as they are biovailable on injested microplastic particles. Illegal levels of Cd were found in all fish as well as some containing dangerous Pb and Cr levels. Cd showed a positive correlation with fish length whereas Pb showed a negative one. The presence of plastic and metals across species and trophic levels may pose a threat to their health and consumption of these fish and their predators causes concern of potential impacts on humans. These risks should be evaluated in future studies, focusing on higher trophic levels to improve understanding of the affects of marine pollution on ecosystems and humans.
A poluição marinha tem atraído uma atenção crescente de cientistas e do público nos últimos anos devido ao seu impacto ambiental cada vez mais percetível. Um dos exemplos é o plástico é omnipresente no ambiente marinho, onde a sua introduçãotem vindo a aumentar continuamente nos últimos anos. Isso significa que a quantidade de plástico que chega ao oceano e, portanto, a incidência do impacto na vida marinha também está a aumentar, na forma de macro como de microplásticos levando à ingestão de plástico. Os estudos têm-se concentrado sobre a quantificação da presença de plásticos e contaminantes dissolvidos, incluindo metais na água e em organismos, incluindo peixes. O plástico encontrado e quantificado em vários locais do mundo tem sido ingerido por vários organismos marinhos. A ingestão de plástico pode causar problemas na saúde dos organismos, como danos internos e bloqueio gástrico, mas também impactos secundários associados aos metais e poluentes orgânicos que são absorvidos na sua superfície. As propriedades dos microplásticos encontrados no oceano, nomeadamente a sua grande superfície em relação ao volume e a degradação que sofrem devido às condições ambientais, tornam provável a adsorção de metais na sua superfície. Estes metais podem então ser acumulados nos tecidos dos peixes. Se acumulados em grandes quantidades, metais não essenciais podem interferir nos processos metabólicos, reduzindo a saúde do animal. A ligação entre o modo pelo qual a poluição afeta diferentes aspetos do oceano são frequentemente negligenciados. O plástico presente na água do mar que foi ingerido pelo peixe, e os contaminantes existentes na superfície desse plástico podem ser acumulados nos seus tecidos dependem um do outro, mas poucos estudos os vinculam. A deteção e quantificação dos plásticos têm-se concentrado em muitas áreas da zona costeira e do oceano aberto, mas, apesar de estarem localizadas no Gyre do Atlântico Norte, o plástico presente nas Bermudas nunca foi estudado na água ou em peixes da zona. Portanto, uma abordagem multifacetada para analisar a poluição marinha provocada pelos plásticos foi projetada para avaliar o impacto na água e nos peixes das águas das Bermudas para fornecer uma visão geral da situação da poluição marinha no país. As redes de arrasto de superfície foram usadas para determinar a densidade do plástico na superfície do oceano, tanto em locais costeiros como no exterior da ilha das Bermudas. Foram amostrados três locais onde foi avaliado quanto a biodisponibilidade de seis contaminantes metálicos (Zn, Cu, Cr, Cd, Pb e Ni), digerindo-o numa solução projetada para imitar as condições intestinais de um peixe. A solução foi então analisada usando Espectrofotometria de Absorção Atômica (EAA). Oito espécies de peixes em três níveis tróficos, variando de pequenos peixes planctivoros a predadores pelágicos maiores, foram recolhidos e dissecados quanto à presença de plástico no seu trato intestinal. O conteúdo intestinal foi digerido em hipoclorito de sódio e analisado ao microscópio para identificar a presença de plástico. Duas dessas espécies, Decapterus macarellus e Harengula humeralis, comercialmente mais valiosas e frequentemente consumidas por seres humanos nas Bermudas e no mundo todo, foram selecionadas para investigar o nível de contaminantes metálicos no tecido muscular dos peixes. Essa é a parte do peixe que é consumido pelos seres humanos, representando, portanto, o maior risco. Amostras de tecido muscular de 17 peixes foram digeridas em ácido nítrico e os níveis de metais analisados através do uso de EAA. O plástico encontrado na superfície do oceano variou entre 30.000 a 130.000 partículas / km2, 89% das quais eram microplásticas. Não foi encontrada diferença significativa entre os locais offshore e costeiros. Todas as oito espécies de peixes e 32% dos peixes individuais continham plástico, 92% dos quais eram microplásticos. A espécie que ingeriu mais plástico foi D. macarellus, uma espécie de alimentação superficial e de um grupo trófico de nível médio. As partículas encontradas foram menores que 14 mm, portanto é pouco provável que causem bloqueio gástrico, mas ainda podem causar lesões no intestino e efeitos secundários de contaminantes associados. O número de peças microplásticas encontradas no intestino dos peixes aumentou com o comprimento e o nível trófico. Essa bioacumulação e causa preocupação para espécies maiores e potencialmente para os seres humanos que frequentemente consomem esses peixes. A análise da EAA mostrou que contaminantes metálicos aderidos a partículas microplásticas ou adicionados durante a fabricação estão biodisponíveis para os peixes após digestão no intestino, permitindo que eles se acumulem nos tecidos do peixe. Os metais foram encontrados nos tecidos musculares de todos os peixes analisados. Níveis acima do valor legal de Cd foram encontrados em todos os peixes, e alguns que continham níveis perigosos de Pb e Cr. O Cd mostrou uma correlação positiva com o comprimento dos peixes, enquanto o Pb mostrou uma correlação negativa. Todos os outros metais não tiveram relação significativa com o comprimento do peixe. Os metais não essenciais, como Cd e Pb, têm a capacidade de afetar os processos metabólicos em peixes. Se os níveis de poluição continuarem a aumentar, a acumulação de metais nos peixes pode ter efeitos nocivos para a saúde e ter impacto no meio ambiente em geral. O consumo desses peixes em grandes quantidades pelos seres humanos pode potencialmente colocar as pessoas em risco de terem problemas de saúde associados a altos níveis de Pb e Cd, incluindo funções cerebrais e renais reduzidas. Os padrões na densidade microplástica na superfície do oceano foram difíceis de determinar, portanto considera-se que uma amostragem mais frequente ajudaria a revelar padrões espaciais ou temporais que poderiam ajudar a compreender o impacto do plástico ao redor das Bermudas. Tendo comprovado a presença de detritos plásticos e contaminantes metálicos no ambiente e na biota das Bermudas, pode dizer –se que esses aspetos devem ser analisados em maior profundidade no futuro para determinar em que medida estão a afectar o ambiente marinho como um todo. A presença de microplásticos e metais nas espécies e nos níveis tróficos pode representar uma ameaça à sua saúde humana devido ao consumo de peixes e seus predadores, causando preocupação de possíveis impactos sobre os seres humanos. Estudos adicionais sobre peixes comercialmente valiosos de níveis tróficos mais elevados apresentariam uma visão mais clara da ameaça a que os seres humanos estão expostos pelo consumo de peixes contaminados. Uma compreensão mais ampla dessas questões permitiria aos governos implementar leis apropriadas que visem proteger a saúde humana e a saúde dos oceanos como um todo.

AbstractThe concern that in nature, ingestion of microplastic (MP) increases exposure of organisms to plastic-associated chemicals (the ‘MP vector effect’) plays an important role in the current picture of the risks of microplastic for the environment and human health. An increasing number of studies on this topic have been conducted using a wide variety of approaches and techniques. At present, the MP vector effect is usually framed as ‘complex’, ‘under debate’ or ‘controversial’. Studies that critically discuss the approaches and techniques used to study the MP vector effect, and that provide suggestions for the harmonization needed to advance this debate, are scarce. Furthermore, only a few studies have strived at interpreting study outcomes in the light of environmentally relevant conditions. This constitutes a major research gap, because these are the conditions that are most relevant when informing risk assessment and management decisions. Based on a review of 61 publications, we propose evaluation criteria and guidance for MP vector studies and discuss current study designs using these criteria. The criteria are designed such that studies, which fulfil them, will be relevant to inform risk assessment. By critically reviewing the existing literature in the light of these criteria, a weight of evidence assessment is provided. We demonstrate that several studies did not meet the standards for their conclusions on the MP vector effect to stand, whereas others provided overwhelming evidence that the vector effect is unlikely to affect chemical risks under present natural conditions.

Microplastics are plastics with smaller than 5mm particle size and they originate from sequential degradation of larger plastic molecules or are manufactured, and they have found use in many realms of life. Their gradual degradability and ingestion by aquatic organisms have become an environmental concern. Microplastics are regarded as a “tiny problem” requiring massive attention. Occurrences of microplastics have been detected in almost all environment matrices. Although several committees have taken steps towards handling the menace, most of the regulations' guidelines refer to “all wastes” in general, leaving many loopholes. This chapter views microplastics, occurrences, detection, and existing policies. The roles of industry and individuals in preserving the ecosystems are deliberated. In summary, emphasis on the bottom-up strategy to curb the escalating amount of plastics waste in our environment is sought and adoption of the “avoid the avoidable” attitude for a more holistic approach in tackling the severity of the impending threat.

Microplastic pollution is a global issue that has a detrimental effect on the food chain in the marine ecosystem. They are found in their highest concentrations along coastal lines and within mid-ocean gyres. In marine environments, microplastics are a threat to marine organisms, as they are often in the same size range as prey and are mistaken as food. When ingested can have a deleterious range of effects on marine organisms, a process which may facilitate the transfer of chemical additives or hydrophobic waterborne pollutants to aquatic lives. In this chapter, we looked at the risk of microplastic pollution and its impact on marine organisms and humankind. The study shows that consumption of microplastics has led to ingestion of chemical toxins in aquatic fish, which leads to damage of digestive organs, choking of marine organisms, channel for the spread of microbes, and a reduction in growth and reproductive output. These threats increase the risk to aquatic fishes and human survival. Hence, the need to educate the public on the dangers of using products that pose an immediate and long-term threat to the marine ecosystem and the health of its organism, and the food we eat by marine scientists.